Overview of the patients and leads
We conducted an entirely concentrated search on the documents of all patients who had undergone epicardial lead implantation in the Shaheed Rajaie Cardiovascular, Medical & Research Center during 2015-2018. All documentations were retrospectively reviewed. According to a systematic search on previous studies on epicardial leads,1,2 the following data were selected and extracted from the documentation regarding each patient; age, sex, past medical history of congenital heart disease (CHD) with exact type. The following epicardial lead characteristics were also reviewed and extracted, including indication for pacemaker implantation, symptoms before implantation, lead type (unipolar non-steroid-eluting and bipolar steroid-eluting), brand (Medtronic and St. Jude), device type (CRT, PPM-DR, and PPM-SR), pace location (atrial, and left ventricular, and right ventricular), pacing mode (DDD, DDDR, VDD, VVI, VVIR). For the 11 patients who had more than one-time epicardial lead implantation (10 patients with two and one had three), their second and third lead was also enrolled as a new lead, and its characteristics were recorded. As a result, for 77 patients in the study, 89 leads were enrolled. Furthermore, the electrocardiogram (ECG), and echocardiogram (echo) of the patients after each lead implantation were obtained, and their data was reviewed, and extracted by an expert. ECG data consisted of V1 R/S greater than 1 (yeas or no), QRS Duration (millisecond or ms.), and notch position. Echocardiographic data included left ventricular end diastolic diameter (LVEDd), left ventricular end systolic diameter (LVESd), and left ventricular ejection fraction (LVEF).